diff --git a/src/schema/controller.capnp b/src/schema/controller.capnp
index fd4b80f..12780d5 100644
--- a/src/schema/controller.capnp
+++ b/src/schema/controller.capnp
@@ -37,6 +37,9 @@ enum OPCode {
   steppingDown   @26;
   replSnapshot   @27;
   replCatchUpDone @28;
+  replConfig      @29;
+  replConfigPush  @30;
+  upgradeConfig   @31;
 }
 
 struct PeerInfo $C.mapname("xce_peerinfo_t") {
@@ -544,7 +547,10 @@ struct RequestReply $C.mapname("xce_reply_t"){
     debugmsg     @4: Text;
     getdata      @5: Data;
     jobid        @6: UInt64;
-    clusterconf  @7: ClusterConf;
+    clusterconf            @7: ClusterConf;
+    replConfigReplyMsg     @8: ReplConfigReply;
+    replConfigPushReplyMsg @9: ReplConfigPushReply;
+    upgradeConfigReplyMsg  @10: UpgradeConfigReply;
   }
 }
 
@@ -601,7 +607,11 @@ struct Request $C.mapname("xce_request_t"){
     runtaskmsg      @18: RunTask;
     preasonmsg      @19: PendReasonSet;
     clrpreasonmsg   @20: ClearPReason;
-    hostctrlmsg     @21: HostControl;
+    hostctrlmsg              @21: HostControl;
+    replConfigRequestMsg     @22: ReplConfigRequest;
+    replConfigPushRequestMsg @23: ReplConfigPushRequest;
+    upgradeConfigRequestMsg  @24: UpgradeConfigRequest;
+    heartbeatmsg             @25: HeartbeatMsg;
   }
 }
 
@@ -674,6 +684,7 @@ struct ClusterConfig $C.mapname("cluster_config_t") {
   xstrings               @17: HashZArrayConfig;
   hproviders             @18: List(ScalerConfig) $C.mapname("hproviders") $C.maplistcount("nhproviders");
   limits                 @19: List(LimitConfig) $C.mapname("limits") $C.maplistcount("nlimits");
+  configGeneration       @20: UInt64 $C.mapname("config_generation");
 }
 
 # ── Persistence configuration (Part 2.6) ────────────────────────────
@@ -703,6 +714,45 @@ struct SnapshotHeader $C.mapname("capnp_snap_hdr_t") {
   headerChecksum @8 :UInt32;
 }
 
+# ── Config replication message structs ──────────────────────────────
+struct ReplConfigRequest $C.mapname("repl_config_req_t") {
+  versionTag  @0: UInt64 $C.mapname("version_tag");
+}
+
+struct ReplConfigReply $C.mapname("repl_config_reply_t") {
+  upToDate    @0: Bool   $C.mapname("up_to_date");
+  versionTag  @1: UInt64 $C.mapname("version_tag");
+  sha256      @2: Data   $C.mapname("sha256");
+  bytes       @3: Data   $C.mapname("bytes");
+}
+
+struct ReplConfigPushRequest $C.mapname("repl_config_push_req_t") {
+  versionTag  @0: UInt64 $C.mapname("version_tag");
+  sha256      @1: Data   $C.mapname("sha256");
+  bytes       @2: Data   $C.mapname("bytes");
+}
+
+struct ReplConfigPushReply $C.mapname("repl_config_push_reply_t") {
+  accepted    @0: Bool   $C.mapname("accepted");
+  versionTag  @1: UInt64 $C.mapname("version_tag");
+}
+
+struct UpgradeConfigRequest $C.mapname("upgrade_config_req_t") {
+  bytes   @0: Data   $C.mapname("bytes");
+  sha256  @1: Data   $C.mapname("sha256");
+}
+
+struct UpgradeConfigReply $C.mapname("upgrade_config_reply_t") {
+  versionTag  @0: UInt64 $C.mapname("version_tag");
+  error       @1: Text   $C.mapname("error");
+  ackedCount  @2: UInt32 $C.mapname("acked_count");
+}
+
+struct HeartbeatMsg $C.mapname("heartbeat_msg_t") {
+  senderPriority @0: UInt32 $C.mapname("sender_priority");
+  term           @1: UInt64 $C.mapname("term");
+}
+
 # ── WAL replication envelope (Part 6 — NOT the on-disk format) ───────
 # Named ReplEnvelope to avoid collision with the on-disk wal_entry_hdr_t.
 struct ReplEnvelope $C.mapname("capnp_repl_envelope_t") {